The present invention relates to a rotary compressor, and more particularly, to a vane-type rotary compressor adapted to be used as an air conditioning compressor of a vehicle.
In general, a rotary vane compressor comprises a cylinder, a rotor rotatably mounted within the cylinder and cooperating with an inner peripheral surface of the cylinder to form a compression chamber therebetween, two side plates for closing both ends of the cylinder, and at least one vane slidably mounted to the rotor for reciprocating movement toward and away from the rotor and dividing the compression chamber into a plurality of compression spaces.
In a conventional rotary vane compressor of the above-mentioned type, as disclosed in, for example, Japanese Patent Unexamined Publication Nos. 61-201896 and 53-106914, the vane is provided at its ends with sub-vanes slidably mounted thereon, and the volume of the compression chamber formed between the outer peripheral surface of the rotor and the inner peripheral surface of the cylinder is increased or decreased as the vane and sub-vanes are rotated along with the rotor, thereby feeding or discharging the pressurized fluid. Further, in this conventional rotary vane compressor, blow-by gas is introduced from the compression chamber to a space in a central portion of the rotor to flow the blow-by gas through the clearances formed between the vanes and the rotor, thereby lubricating the slidingly contacting surfaces of the vanes and rotor. Further, in order to prevent the back flow of the fluid from leaking from between the ends of the vane and the inner peripheral surface of the cylinder, the pressure was applied to the backs of the vane and sub-vanes. Particularly, with respect to the sub-vanes, on the basis of the fact that higher pressure in a higher pressure space between two compression spaces adjacent to the vane and sub-vanes flows into a lower pressure space through the clearances formed between the vane and the sub-vanes, a part of said higher pressure flowed into said lower pressure space was introduced into the back of the sub-vanes, thereby providing sealing pressure.
However, in this conventional rotary vane compressor, when the vanes are in a compression stroke the pressure acting on the back of the sub-vanes is sufficiently high, but, when the vanes are in a suction stroke such pressure is relatively low. Consequently, in the suction stroke, the pressure sufficient to provide the proper sealing pressure for the sub-vanes cannot be obtained, which occurs a problem when the rotor is rotated at a low speed in that the efficiency of the seal between the sub-vanes and the inner peripheral surface of the cylinder is reduced, thus increasing loss of leakage of the fluid.
U.S. Pat. No. 3,945,775 discloses a construction that the sub-vanes themselves are pressed against the inner surface of the cylinder.
However, according to such construction, since the sub-vanes are always subjected to the pressure due to a spring force, a strong spring is necessary to provide the constant higher pressure, and there is a larger mechanical loss.
Further, since the pressure is obtained from the spring, the number of parts inevitably increase, and, therefore, reliability of operation of the compressor is decreased.